Generally, the DEMOS devices may be employed for applications such as power switching circuits. The DEMOS devices may include a drain extension region which substantially increases operating voltages for the devices.
FIG. 1 is a cross-sectional view illustrating a conventional DEMOS device.
Referring to FIG. 1, a conventional DEMOS device 10 may include a gate structure 20 formed on a substrate 12, drift regions 30 and 32 formed at surface portions of the substrate 12 adjacent to both sides of the gate structure 20, and source/drain regions 40 and 42 formed at surface portions of the drift regions 30 and 32.
Further, a gate spacer 22 may be formed on side surfaces of the gate structure 20, and insulating layer patterns 50 and 52 used as silicide blocking layers may be formed on the drift regions 30 and 32 and the gate spacer 22.
Meanwhile, when driving voltage and drain voltage are applied to the gate structure 20 and the drain region 42, respectively, impact ionization may occur in the drain region 42 and/or the drift region 32 adjacent to the drain region 42 due to electrons with sufficient kinetic energy. In detail, a lateral electric field generated by the drain voltage may provide electrons with sufficient kinetic energy between the source region 40 and the drain region 42, and new electron-hole pairs may thus be produced by the impact ionization in the drain region 42 and/or the drift region 32. Particularly, leakage current of the DEMOS device 10 through the substrate 12 may be increased by the impact ionization.